Method of producing printing-plates.



OTTO LUPPE, OF MUNICH, GERMANY.

METHOD OF PRODUCING PRINTING-PLATES.

No Drawing.

To all whom it may concern:

Be it known that I, O'rro Lnrrn, a subject of the German Emperor, residing at Munich, Germany, have invented certain new and useful Improvements in Methods of Producing Printing-Plates, of which the following is a specification.

My invention relates to a novel method of producing printing plates, and is particularly applicable to plates in which a resinous layer, which forms the acid resistant or resist during the etching action, is interposed between the plate proper and the sensitized film. In the preparation of such plates, the usual procedure heretofore has been to clevelop the printed plate whereby the parts of the sensitized film unaffected by the light are dissolved, and then by means of a suitable solvent to remove from the plate the light-affected parts of the sensitized film and the resinous resist thereunder.

One of the principal objects of my invention is to dispense with the use of chemical solvents to efiect the removal of the light afiected parts of the sensitized film and corresponding parts of the resist.

A further object of my invention is to very materially simplify the method of preparing such plates for etching, thus efiecting a. substantial saving in time, labor and cost.

Other objects of the invention, and the manner of practising the same will be clearly set out in the following specification.

The invention consists, essentially, in subjecting the developed photographic film to a tanning action, and thereupon removing the light-afiected parts of the sensitized film and the resinous layer thereunder.

To prepare a plate for etching, according to my invention, I proceed as follows :A plate of any suitable material, such as metal, is coated with a layer of any resin which while being insoluble in water is soluble in alcohol, esters or hydrocarbons generally, and after being applied will set sufficiently to receive a sensitized film and resist acids during etching. YVhe-n the resinous layer is dry I apply thereto a film of sensitized material, usually of size, fish-glue, gelatin or gum-arabic or composition. The plate is then exposed to the action of light through the desired negative, and is thereupon developed, as a result of which the parts of the film not acted upon by the light, are dissolved and removed from the plate. The

Specification of Letters Patent.

Application filed May 20,1911.

Patented Nov. at, 1913.

Serial No. 628,410.

several steps so far described are those usually employed in the preparation of plates of this character.

After the plate has been developed in the manner above referred to I subject the remaining part of the film, that part which has been affected by the light, to a strong tanning action, using for that purpose any appropriate tanning material, such as chromic acid, alum, chromic alum, log-wood, formaldehyde or the like. The prepared plate is then preferably washed in water and thoroughly dried.

After the tanning, washing and drying, the film is subjected to the action of a hygroscopic fluid for the purpose of extracting all residue of moisture from the film and making it hard and brittle. The hygroscopic fluid which I prefer to employ is glycerin to which is preferably added a tanning material such as tannic acid or formaldehyde. As a result of the treatment with glycerin the light-affected part of the film immediately separates from the plate and takes with it the resinous layer lying thereunder. The plate is then washed and is in condition for etching, no preliminary treatment of any kind being required. While, ordinarily, hygroscopic fiuids such as glycerin tend to soften gelatin or size, the effect is exactly the reverse if the gelatin or size has been previously tanned, and I have found that by subjecting the sensitized film to the action of glycerin, the latter extracts all residue of moisture from the film and makes it harder and more brittle than after the tanning action, and as a result of such increased hardness and brittleness the film automatically separates from the plate.

By means of my invention, the plate is ready for etching immediately after the treatment with glycerin, and no preliminary heating to bake in the resist is required. Inasmuch as the use of heat is dispensed with I may employ plates made of materials which, owing to their inability to withstand high temperatures, are not ordinarily adapted for the purpose.

Another important advantage of my in vention is that I dispense with the use of all chemical resin solvents which, when used, frequently seep between the film and the resist and remove the latter in places where it should not be removed.

What I claim as my invention is The herein described method of producing printing plates Which consists in coating the surface of the plate With a resinous composition, applying thereto a sensitized gelatin film, subjecting said film to the action of light and developing the same, subjecting the light-affected portion of said film to a tanning action and then to the action of a hygroscopic fluid adapted to render such light-afl'ected part hard and brittle, Whereby it and the resinous layer therebeneath 10 Will separate from said plate, and finally etching the plate.

In testimony whereof I have aflixecl my signature in presence of two Witnesses.

OTTO LUPPE. Witnesses:

ARTHUR V. W. COTTER, MATHILDE K. HELD.

copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents.

Washington, D. G. 

